Laminar-turbulent transition in channel flow: wall effects and critical Reynolds number

This article describes a possible cause of natural laminar-turbulent transition in channel flow, and the minimum critical Reynolds number Rc,min is determined. It is assumed that the mechanism of transition is the same for both circular pipe flow and channel flow since each flow has its own minimum critical Reynolds number. Our starting points are that under natural disturbance conditions, transition appears to take place only in the developing entrance region and that the critical Reynolds number Rc becomes Rc,min when using a sharp-edged uniform channel. In our previous studies of circular pipe flow, we have developed a model for transition and obtained Rc,min=1910 and 1950 in two mesh systems. In this study, for channel flow, the above transition model is verified by obtaining Rc,min=1190 and 1260 in two mesh systems.